Question 1

Which of the following best defines a virus?

Accepted Answer

An acellular, obligate intracellular parasite composed of nucleic acid in a protein shell.

Question 2

Which structural feature distinguishes an enveloped virus from a nonenveloped (naked) virus?

Accepted Answer

Presence of a lipid bilayer derived from the host cell membrane.

Question 3

A virus with a segmented, single-stranded (−) RNA genome and 8 segments is most likely:

Accepted Answer

An influenza virus

Question 4

Which of the following statements about viral genomes is correct?

Accepted Answer

Viral genomes can be single- or double-stranded DNA or RNA.

Question 5

During the lytic cycle of a bacteriophage, which event occurs immediately after penetration of the host cell?

Accepted Answer

Degradation of host DNA

Question 6

Which of the following best describes the function of glycoprotein spikes on a viral envelope?

Accepted Answer

They function in host recognition and attachment.

Question 7

A virus that infects only human T helper cells but not other cell types demonstrates which property?

Accepted Answer

Narrow host range and high host cell specificity

Question 8

Which of the following is a key difference between the lytic and lysogenic cycles of bacteriophage infection?

Accepted Answer

The lysogenic cycle involves integration of viral DNA as a prophage, while the lytic cycle results in immediate host cell lysis.

Question 9

Which of the following best explains why viruses are considered obligate intracellular parasites?

Accepted Answer

They require host cell machinery for replication and metabolism.

Question 10

A (+) RNA virus genome can directly serve as:

Accepted Answer

A template for translation to produce viral proteins

Question 11

Which of the following is NOT a component of all viruses?

Accepted Answer

Envelope

Question 12

Which step in the viral life cycle is responsible for the release of progeny virions to infect new host cells?

Accepted Answer

Exit and transmission

Question 13

A scientist discovers a new virus with a polyhedral capsid, a single-stranded RNA genome, and no envelope. Which of the following is most likely true about this virus?

Accepted Answer

It is a naked virus and may be more resistant to environmental stress than enveloped viruses.

Question 14

Which of the following best describes the process of transduction in the context of bacteriophage lysogeny?

Accepted Answer

Transfer of bacterial genes from one cell to another via a bacteriophage.

Question 15

Which of the following equations best represents the relationship between the number of viral genomes ($N$), the number of infected host cells ($C$), and the average burst size ($B$) in a lytic infection?

Accepted Answer

$N = C 	imes B$

Question 16

Which of the following is a real-world consequence of the segmented genome of influenza viruses?

Accepted Answer

They can undergo genetic reassortment, leading to new viral strains.

Question 17

Which of the following is a correct statement about the function of viral genes?

Accepted Answer

They code for structural components and enzymes used in the viral life cycle.

Question 18

A temperate bacteriophage is characterized by which of the following?

Accepted Answer

It can integrate its genome into the host chromosome as a prophage.

Question 19

Which of the following is a key criterion used in the classification of viruses?

Accepted Answer

Genome type (DNA or RNA, single- or double-stranded) and presence or absence of an envelope

Question 20

Which of the following best explains why lysogenic cells are immune to reinfection by the same phage?

Accepted Answer

The prophage expresses genes that prevent superinfection.

Viruses, Viroids, & Prions: Structure, Classification, and Life Cycles

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